Rotary drum structure for a sterilizing apparatus

ABSTRACT

The invention relates to a rotary drum structure for a sterilizer. The structure includes: four beams (30, 32, 34, 36) disposed parallel to said axis and defining a rectangular parallelepiped volume; a plurality of spacer elements (52, 54, 56) disposed in the four faces defining said parallelepiped volume and forming triangulated structures; a second end part (60) fixed to second ends of the beams to define an inlet opening (64) into said drum; and a circular running path (62).

The present invention relates to a rotary drum structure for asterilizer of the rotary drum type.

Objects or products in the food and pharmaceutical industries, such asboxes, jars or dishes, flasks, etc. are often sterilized in so-calleddiscontinuous sterilizers or autoclaves into which the products to betreated are inserted and from which they are extracted after theintended treatment cycle. Such products to be treated are disposed inbaskets, stackable trays, or other similar storage elements.

For some such products, sterilization heat treatment must be performedwhile the product is being stirred within its packaging. Stirring isproduced by rotating a drum inside the sterilizer, which drum enclosesbaskets filled with the packages of products to be sterilized that arecontained therein. The same type of problem arises when it is desired todrip or tilt certain products into an autoclave type of device which isthen referred to as a dripper or a tilter. This operation makes itpossible to remove the water deposited on the products by gravity duringsterilization.

Patent application WO-A-93/04707 describes a rotary drum autoclave orsterilizer, and in particular means for holding baskets inside therotary drum.

Accompanying FIG. 1 is a perspective view of the known way ofimplementing the rotary drum. In this figure, there can be seen aportion of the outer cylindrical case 10 of the sterilizer, and,partially extracted therefrom, the rotary drum assembly 12. The drum 12is constituted by mutually parallel length members 14 constituted bytubes that define the periphery of the drum structure. The tubes 14 passthrough circular sectors such as 16. The length members 14 are welded tothe circular sectors 16 which are made of sheet metal. At the ends ofthis structure, there are to be found firstly a part 18 provided with anopening 20 for receiving baskets, and secondly a part 22 provided withmeans 24 for co-operating with rotary drive means 26 mounted on theenclosure 10. In addition, in this figure, there can be seen partiallyextended rails 28 resting on the bottom portion of the structure toenable baskets to be inserted and removed, which baskets contain theproducts to be treated.

That structure suffers from numerous drawbacks. Firstly, its lifetime isrelatively short because of fatigue stresses of greater or lesserextent, because of the high rate at which treatment installations areused, and because of ever-increasing loads installed therein. Also, thattype of structure is incapable of achieving a high degree of mechanicalstrength, thus giving rise to phenomena associated with bending,twisting and/or shear between the various component elements of thedrum.

Such deformation has non-negligible effect on the efficiency of devicesfor holding objects that are secured to the structure. As a result thereare high maintenance costs because of the frequent down times of themachine. Finally, such structures are heavy, thereby consuming a largeamount of electrical energy in rotating the drum.

An object of the present invention is to provide a rotary drum structurefor a rotary drum autoclave or sterilizer that has a structure which islighter in weight and above all of greater stiffness and thus longerlifetime.

To achieve this end, the rotary drum structure for a sterilizercomprising an outer case having a longitudinal axis about which saiddrum is mounted to rotate is characterized in that it comprises:

four beam-forming elements disposed parallel to said axis and defining arectangular parallelepiped volume;

a plurality of spacer elements disposed in the four faces defining saidparallelepiped volume, each spacer element having a first end welded toone beam element and a second end welded to another beam element lyingin the same face, the spacer elements and the beams forming triangulatedstructures;

a first end part fixed to a first end of the beam elements to define arotary bearing disposed on said axis for rotation;

a second end part fixed to a second end of the beam elements to definean inlet opening into said drum; and

means forming a circular running path secured to said beam elements,said running path having said axis for rotation as its axis ofrevolution, said running path being adapted to co-operate with rotaryguide means secured to the inside face of the outer case of saidsterilizer.

It will be understood that the above all-welded mechanical structuremade up of four longitudinal beams interconnected by an all-weldedstructure constituted by spacers which preferably form a "triangulated"structure, there is obtained firstly very great overall stiffness forthe structure with a high degree of resistance to bending, twisting, andshear, while simultaneously obtaining a structure of reduced weightgiven its mechanical qualities.

Other characteristics and advantages of the present invention appearmore clearly on reading the following description of an embodiment ofthe invention given by way of non-limiting example. The descriptionrefers to the accompanying figures, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is already described above and is a perspective view of a priorart sterilizer rotary drum;

FIG. 2 is a perspective view of the drum structure of the invention;

FIG. 3 is a half elevation view of the front part defining the openingof the drum;

FIG. 4 is a one-fourth elevation view of the rear part serving to definethe axis of rotation of the drum;

FIG. 5 is a side view in section of the rear part; and

FIG. 6 is an axial section view of an autoclave or sterilizer includinga rotary drum of the invention.

The drum structure of the invention is described, initially withreference to FIG. 2. The drum structure essentially comprises fourlongitudinal beams 30, 32, 34, 36 disposed parallel to the axis ofrotation of the drum. These four beams define a rectangularparallelepiped whose cross section is square or rectangular. Each topbeam, i.e. the beams 30 and 32, comprises a web 38 and two fixingflanges 40 and 42. The cross section of the bottom beams 34 and 36 ismore complex in that their webs 44 also define respective horizontalportions 46 having a function that is explained below. The bottom beamsalso have pairs of fixing flanges 48 and 50.

As can also be seen in FIG. 2, two beams defining the same face of therectangular parallelepiped are interconnected by spacer-formingelements, or more precisely by a triangulated structure. These spacersare preferably constituted by alternating crossed diagonals such as 52and 54, e.g. formed by flat bars, and crossmembers 56, e.g. constitutedby channel section bars. The ends of each spacer 52, 54, 56 are weldedto the flanges 40 and 42 of the top beams or 50 and 48 of the bottombeams. A structure is thus obtained which is very stiff and of weightthat is relatively small given its stiffness. It will also be understoodthat it is easy to provide beams of a different length to adapt thelength of the drum to the dimensions of the autoclave without thataltering the general structure of the drum.

It is also clear that the spacers interconnecting longitudinal beamscould be of a shape other than that shown in FIG. 2. The triangulateddisposition and shape of the spacer assemblies must be designed as afunction of the conditions in which the sterilizer is to be used so asto achieve the desired degree of stiffness.

As can also be seen in FIG. 2, the above-described structure furthercomprises a front part 60 which can be seen more clearly in FIG. 3. Thefront part 60 has a circular periphery 62 and an inside cutout 64 thatpreferably constitutes the opening of the drum. The shape of the insidecutout 64 naturally corresponds to the respective sections of the topbeams 30 and 32 and of the bottom beams 34 and 36. The sheet metalforming the front part 60 is preferably fixed to the structureconstituted by the beams and the various spacers by means of angle barssuch as 66. These various parts are preferably assembled together bybolts. In a preferred embodiment, the front part 60 is provided aroundits periphery with a cylindrical flange 68 having the axis of rotationof the drum at its own axis of revolution. This cylindrical flange 68constitutes a running path for guiding the drum in rotation inside theouter case of the sterilizer, as explained below.

At its other end, the drum structure is provided with a rear part givenreference 70 and shown in greater detail in FIGS. 4 and 5. This rearpart serves to connect a hub for driving the drum in rotation to theremainder of the drum structure. This part 70 comprises an outercircular ring 72 which is connected to an inside portion 74 that formsthe hub by means of a skin or web 76 that extends between the peripheryof the hub and the outer ring 72.

As shown diagrammatically in FIG. 5, a rotary drive shaft 78 passingthrough the end wall of the sterilizer case is engaged in the hub 74. Asalso shown in FIG. 5, the outer ring 72 is secured to metal sheet 80which is itself secured to the end of the drum structure.

The rear part 70 is preferably bolted to the triangulated structure ofthe drum.

In FIG. 6, there can be seen the sterilizer as a whole including thedrum as described with reference to FIGS. 2 to 5, which drum is givenoverall reference 82. In this figure, there can also be seen the outercylindrical case 84 of the sterilizer, its sealed front door 86, and itsend wall 88. Through the end wall 88, there is shown in simplifiedmanner a passage for the rotary drive shaft 90 that co-operates with therear part 70 of the drum. The figure also shows wheels such as 92 forproviding rotary guidance that are mounted inside the outer enclosure 84and that co-operate with the running path 68 of the front part 60 of thedrum. Also shown in this figure, in simplified manner, are guide railsfor trays inserted into the drum, referenced 94, and mounted on thehorizontal portions 46 of the webs of the bottom beams 34 and 36.Finally, this figure also shows presser plates 96 which serve to holdstationary and keep in rotation the baskets once they have been insertedinto the drum. These presser plates are controlled by systems comprisingactuators 98 and levers 100 as described in detail in theabove-mentioned PCT patent application.

It should be observed that given the way in which the substantiallyplane top face of the drum is implemented, installation of the presserplates is facilitated compared with prior art drums where the generalshape is cylindrical. In addition, the great stiffness of the structureensures greater effectiveness of the presser plates and more uniformpressing force.

Naturally, it would not go beyond the invention to provide thelongitudinal beams of the drum with cross sections other than thoseshown in FIG. 2. Also naturally, the triangulated structure constitutedby spacer elements could be given some other configuration adapted tothe particular mechanical stresses on a drum.

Also naturally, the running path 68 need not be fixed to the peripheryof the end part 60, but could be secured to an intermediate portion ofthe beams 30 to 36. The open end of the drum would then be cantileveredout.

Also naturally, a plurality of running paths 68 could be provided thatare spaced apart along the length of the drum to provide even betterrotary guidance and to avoid any risk of bending in the event of theload to be treated being large.

I claim:
 1. A rotary drum structure for a sterilizer including an outercase having a longitudinal axis about which the drum is mounted torotate, the structure comprising:four beam-forming elements disposedparallel to said axis and defining a rectangular parallelepiped volumefor receiving objects to be sterilized; a plurality of spacer elementsdisposed in the four faces defining said parallelepiped volume, eachspacer element having a first end welded to one beam element and asecond end welded to another beam element lying in the same face, thespacer elements and the beams forming triangulated structures; a firstend part fixed to a first end of the beam elements to define a centralrotary bearing disposed on said axis for rotation, the central rotarybearing disposed in the center of said first end part; a rotary driveshaft adapted to co-operate with said central rotary bearing; a secondend part fixed to a second end of the beam elements to define an inletopening into said drum; and means forming a circular running pathsecured to said second end part, said running path having axis forrotation at its axis of revolution, said running path being adapted toco-operated with rotary guide means secured to an inside face of theouter case of said sterilizer.
 2. A drum structure according to claim 1wherein each of the two beam-forming elements defining the bottom faceof said volume has a respective web defining an internal horizontalguide rail on which to receive objects.
 3. A drum structure according toclaim 1 wherein said spacer elements associated with said pairs of beamelements are constituted by alternating crossed diagonals and crossmembers.
 4. A drum structure according to claim 1 wherein said secondend part is constituted by a plate having a circular periphery and saidrunning path comprises a cylindrical flange secured to the periphery ofsaid plate.
 5. A drum structure according to claim 1 wherein said firstend part comprises a web whose outer periphery is secured to said firstends of said beam-forming elements, and whose inner periphery is securedto hub-forming means.
 6. A rotary drum structure for sterilizingobjects, comprising:four beam-forming elements arranged as aparallelepiped; cross-braces secured between the beam-forming elementsto form triangular structures between adjacent beams, the volume withinthe parallelepiped being generally unobstructed by the cross-braces soas to be capable of freely receiving objects to be sterilizedtherewithin; a first end piece secured to a first end of theparallelepiped; a first drive shaft centrally secured to the first endpiece to rotate and support the parallelepiped thereat; a second endpiece secured to a second parallelepiped end opposite said first end,the second end piece having an aperture through which the objects to besterilized may pass into the volume of the parallelepiped; circularrunning path secured to the parallelepiped; wheels mounted to an outerenclosure, said wheels co-operating with said circular running path toprovide support for the parallelepiped as it rotates.